In processes for manufacturing paper and paperboard (referred to hereinafter as “paper”), it is often desirable to condition a moving paper web between stages of the process, especially between the later stages of drying and subsequent calendering. The conventional process of drying paper involves urging water out of the web by a combination of mechanical and thermal means, i.e., use of vacuum and squeeze rolls along with a dryer unit in which the paper web is carried in serpentine fashion through a series of co-rotating steam-filled cylinders where opposite surfaces of the web are placed in contact with the hot surfaces of the cylinders in rapid alternating succession until the web is dried. As the paper is being dried, boundary layers of hot air tend to develop adjacent the opposite surfaces of the web and within pores of the web, all of which have been found to significantly hinder efforts to cool the web as it proceeds to subsequent calendering or other treatments where a cooled web is desirable.
The difficulties in cooling a paper web proceeding from a dryer unit are becoming more pronounced with the ever-increasing speeds of modern papermaking machines. Accordingly, a significant amount of cooling gas is now often required to not only penetrate the boundary layers of hot gases adjacent the web surface, but also to penetrate into the web pores to displace hot gases therein and thereby effectively and efficiently cool the web.
It is therefore an object of the present invention to provide an apparatus and associated method for conditioning a fibrous web.
Another object of the invention is to provide an apparatus and method for cooling a moving fibrous web.
Still another object of the invention is to provide an apparatus and method for efficiently removing at least a portion of an air boundary layer carried adjacent a fibrous web.
Yet another object of the invention is to provide an apparatus and method for cooling and moisturizing a moving fibrous web.
A further object of the invention is to provide an apparatus and method for efficiently cooling a fibrous web.
An additional object of the invention is to provide an apparatus and method of the character described which is relatively simple and is readily adaptable for use with conventional papermaking machines and processes.